It was rye flour. Ergot is the fungus that grew on the rye. It did indeed affect much of the population, as rye bread was a staple.
I wonder if ergot wasn't the root cause, but those who wanted to be werewolves would seek out the ointment, etc. as well and attributed their 'transformation' to the ointment and chants/prayers - when in reality it was the ergot. How do we know about this ointment/ritual anyhow? Are we (scientists) just surmising what may have happened in that regard, or is there proof? I don't recall.
Muse, I agree about many of these werewolf sites. There isn't a lot to learn there, but plenty of people going on about how they are lycanthopes/therianthropes.
Kell